Ignition system employing controlled-duration continuous-wave high-frequency spark energy

ABSTRACT

An ignition system for internal combustion engines. It generates a controlled-duration continuous-wave high-frequency spark, and employs an output transformer in an oscillator which includes a control winding for starting and stopping the oscillator. There is an electronic switch in series with the control winding; and the spark intervals, including duration thereof, are determined by photoelectric engine-timed means that employ a phototransistor. There is a control circuit for the electronic switch, which circuit includes means for minimizing the response time of the phototransistor.

[75] Inventor:

United States Patent 1191 Canup 1 Oct. 21, 1975 [54] IGNITION SYSTEM EMPLOYING CONTROLLED-DURATION CONTINUOUS-WAVE HIGH-FREQUENCY SPARK ENERGY Robert E. Canup, Chester, Va,

[73] Assignee: Texaco Inc., New York, NY.

[22] Filed: Apr. 11, 1974 [21 Appl. No: 460,243

[52] US. Cl. 123/148 E; 315/209 [51] Int. Cl. H05B 37/02 [58] Field of Search 123/148 E [56] References Cited UNITED STATES PATENTS 3,502,060 3/1970 Tibbs 123/14'8 E 3,512,042 5/1970 Malavasi 123/148 E 3,581,725 6/1971 Hemphill 123/148 E 6/1972 Schuette 123/148 E Ford 123/148 E Wernet 123/148 E Primary ExaminerWendell E. Burns Assistant Examirier-James W. Cranson, Jr. Attorney, Agerit, 0r FirmT. H. Whaley; C. G. Ries; Henry C. Dearborn [57] ABSTRACT An ignition system for internal combustion engines. It generates a controlled-duration continuous-wave highfrequency spark, and employs an output transformer in an oscillator which includes a control winding for starting and stopping the oscillator. There is an electronic switch in series with the control winding; and the spark intervals, including duration thereof, are determined by photoelectric engine-timed means that employ a phototransistor. There is a control circuit for the electronic switch, which circuit includes means for minimizing the response timeof the phototransistor.

13LC Iaims, 3 Drawing Figures US. Patent Oct. 21, 1975 Sheet 1 012 3,913,550

U.S. Patent 0m. 21, 1975 Sheet 2 of2 IGNITION SYSTEM EMPLOYING CONTROLLED-DURATION CONTINUOUS-WAVE HIGH-FREQUENCY SPARK ENERGY CROSS-REFERENCES TO RELATED APPLICATIONS I This invention is related to the following prior applications which define inventions by the same inventor:

Ser. No. 209,060 filed 12-17-71; Ser. No. 246,212 filed 4-2l-72; Ser. No. 263,803 filed 6-19-72; Ser. No. 333,856 filed 2-20-73.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention concerns ignitionsystems in general. More specifically, it relates to an improved ignition system for internal combustion engines, which employs a continuous-wave high-frequency spark generator. The invention is particularly related to improvements for the foregoing type of high-frequency spark-generating system.

2. Description of the Prior Art While there area considerable number of known systems for developing continuous-wave spark signals that are for use in internal combustion engines, and such systems sometimes include the use of photoelectric en- .ginetimed controls for introducing the spark signals,

they have been found to have a drawback in that the photoelectric control introduces a substantial time delay in the initial response. Such a time delay is especially detrimental as high speeds are introduced in the engine, because the delay is relatively constant and, consequently, involves greater crank-angle enginetiming delays as the speed is increased.

Consequently, it is an object of this invention to provide an improvement for the control portion of a highfrequency spark system that involves photoelectric engine-timed controls. The improvement acts to greatly reduce delays caused by response of the photoelectric elements.

Another object of the invention is to provide a system for use with high-frequency continuous-wave spark generators, particularly of the type that employs squarewave oscillators. Such a system has been found to generate large amounts of radio-frequency signals, and since these tend to cause spurious actions in the control system, the elimination of radio-frequency energies from the control system becomes an important feature. I

SUMMARY OF THE INVENTION trol winding for breaking and making a loading circuit which includes said control winding. The said spark intervals are determined by photoelectric engine-timed means including a phototransistor, and the said electronic switch means has a control circuit therefor, including said photoelectric engine-timed means. In relation to the foregoing combination, the invention concerns an improvement which comprises means incorporated with said control circuit for minimizing the response time of said phototransistor.

Again, briefly, the invention concerns an improvement related to a combination with an ignition system for an internal combustion engine, wherein said system employes controlled-duration continuous-wave highfrequency spark energy. The said spark energy is created by a squarewave oscillator having an output transformer, and having a control winding thereon for starting and stopping oscillation of said oscillator at the beginning and endof each spark interval. The combination also comprises electronic switch means connected in series with said control winding for breaking and making a loading circuit which includes said control winding. The said spark intervals are determined by photoelectric engine-timed means comprising a lightemitting diode and a phototransistor. The said electronic switch means has a control circuit therefor which includessaid phototransistor. In combination with the foregoing system, this invention concerns the improvement which comprises first circuit means for connecting said phototransistor in a common collector configuration relative to said control circuit, and second circuit means for connecting the emitter of said phototransistor to the emitter of an input transistor of said control unit. The said second circuit means includes a radio-frequency filter for blocking radiofrequency signals generated by said spark energy. The improvement also comprises third circuit means including a temperature-sensitive resistor for energizing said light-emitting diode, in order to compensate for changes in ambient temperature at the engine-timed means. It also comprises fourth circuit means including said light-emitting diode having a predetermined forward voltage drop, and connecting said diode to the base of said input transistor, all whereby said ignition system has improved response to the enginetimed spark-control means in giving temperature compensation and radio-frequency signal rejection.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects and benefits of the invention will be more fully set forth below in connection with the best mode contemplated by the inventor of carrying out the invention, and in connection with which there are illustrations provided in the drawings, wherein:

FIG. 1 is a schematic circuit diagram illustrating a complete system according to one modification of the invention;

FIG. 2 is another circuit diagram illustrating a different modification of the control-circuit portion of a system like that illustrated in FIG. I; and

FIG. 3 is yet another circuit diagram illustrating only the engine-timedphotoelectric portion of a third modification of the system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, it will be noted that the complete ignition system illustrated includes the basic elements like those shown in one or more of the above-noted copending applications. Consequently, the details of such elements, as the oscillator per se or only the control unit (which have been fully described in those prior applications), need not be again set forth here. It will sufficient to note that the system illustrated in FIG. 1 includes an oscillator 11 that is enclosed within a dashed-line box 12, and-which employs an output above-noted applications Ser. Nos. 209,060; 246,212,

and 333,856.

Similarly, the system-in'cludes'a conventional ignition switch 17 which is shown in a dashed-line box 18 that includes a battery 19 'therein. It will be understood that the physical locations of the battery and ignition switch are usually quite widely separated on an automobile.

The battery 19 supplies power to the oscillator 11 via a permanent circuit connection 22. Also, when the ignition switch 17 is turned on, the battery 19 supplies DC power (via a circuit connection 23) to parallel circuits. One includes a connection 24 for energizing the control winding 14, and the other includes a connection 25 that is for energizing a relay 26 that is shown enclosed in a dashed-line box carrying that reference number. Here again, these elements and the manner of operation thereof have been fully described in one or more of the foregoing applications.

The control winding 14 is in series with an electronic switch, i.e., a transistor 29, which determines whether the winding 14 is AC-short-circuited or not. At the same time, when the transistor 29 is conducting, the circuits include application of a DC bias for creating a core set on the transformer 13. The transistor 29 is controlled for determining whether it is conducting or nonconducting by means of a control circuit 32 that includes all of the circuit elements between the base connection of transistor 29 and the output circuit of a control-circuit-input transistor 35. The elementsof a control circuit like 32 are fully described in the foregoing application Ser. No. 263,803. I

The input transistor 35 is controlled by a photoelectric engine-timed unit 38 that includes a light-emitting diode 39 and a phototransistor 40. It will be appreciated that in the system as illustrated in FIG. 1, the unit 38 will be physically located on the distributor unit of the engine, and there will be included a shutter (not shown) which is driven by a timing shaft (not shown) from the engine so as to determine the engine timed intervals for producing spark energy.

It will be observed that the phototransistor 40 is con-. nected in a common collector configuration relative to the control circuit 32. Thus, while a common collector circuit designation often connotes a grounded collector, in this instance the common circuit to which the collector of phototransistor 40 is connected, is a positive DC circuit that is a common circuit of the control circuit 32. On the other hand, the emitter of phototransistor 40' is connected via a circuit connection 43 to the base of the transistor 35. Transistor 35 has a DC bias applied to it such that it is just below the cut-off point in the absence of any signal from the'emitter of phototransistor 40. Such bias is obtained by having a pair of resistors 46 and 47 connected in series from the com- 7 reduced since only a small voltage rise is needed to cause transistor 35 to conduct.

An ignition system according to this invention may be made operative over a full range of temperature conditions that might be encountered with internal combustion engines, by including in the circuit for energizing the light-emitting diode 39 a temperaturesensitive resistor 53. This is because of the characteristics of light-emitting diodes and phototransistors. Thus, the radiant energy emitted by a light-emitting diode is a function of the current passed through the junction, If too much current is passed through the junction, it will overheat, and the diode will be destroyed. The safe current level of the diode will be determined by the ability of the junction to dissipate heat. Therefore, the safe current at high ambient temperatures is much lower than when the ambient temperature is low. Also, the light-emitting efficiency of the light-emitting diode increases as the junction temperature decreases, so that at low ambient temperatures more radiation will be emitted for the same junction current than when the ambient temperature is increased. In addition, a phototransistor becomes less sensitive as the temperature is descreased, and more sensitive as the temperature rises, which tends to partially compensate for the opposite changing amount of radiation from the lightemitting diode. However, in practice it is found that the total effect is not exactly offsetting, and at low ambient temperatures it is necessary to increase the light-- ture while still maintaining the total or combined sensitivity. At the same time, the reduced current tends to keep the junction cooler which contributes to maintaining the emitting efficiency high.

It has been found that the system using the temperature-sensitive resistor 53 will operate satisfactorily within an ambient temperature range of from about 45 F. to about +237.5 F.

It has been discovered that in the type of continuouswave high-frequency ignition system according to this invention, largely because the oscillator is squarewave in nature, a large amount of radio-frequency energy is generated at the spark gaps during each of the sparking intervals. Such radio-frequency energies are radiated and tend to be applied at various points in the whole circuit. Consequently, there is a tendency to introduce undesired signals after each starting of the oscillator, and these tend to cause reenergization, or continuation of the oscillation beyond the normal stopping thereof. This tends to cause untimed spark ignitions in additon to overloading, and thus tending to burn out various elements of the system, e.g., the electronic switch (transistor) 29.

In order to avoid the foregoing undesired conditions, there is included in the circuits with the input transistor 35 a radio-frequency choke coil 56 located between the emitter of transistor 35 and ground. This prevents 1 radio-frequency-signals from reaching the base of a transistor 64. Also, there is a capacitor 68 connected from the collectorof transistor 35 to ground which shunts radio-frequency signals and, in addition, there is another capacitor 67 connected from the collector of input transistor 35 to the base thereof, which-causes a substantial amount of negative feedback to the radio-. frequency signals. r

In addition to theradio-frequency blocking effects, thereis a coil 57 connected in the outputcircuit of the transistor 35, which is designed to improve the response of the control system to the desiredsignal frequency, e.g., to be resonant atabout 20,000 Hertz. There is a resistor 60 connected acrossthe coil 57 so as to critically damp the'reson'ant effects inorder to prevent any undesired ringing.

FIG. 2 illustrates a modification of the controlunit portion of the syste m, and for the purpose of adequate orientationfthe same basic control circuit 32 as is illustrated in FIG. 1, is shovvn again in FIG. 2. As was indicated above, a typical control circuit like that designated by reference numeral 32, is shown and described in the copending application Ser. No 263,803 which is indicated in the crossreferences. Thus, the transistor 29 is illustrated at the output end of the control cricuit 32 and, of course, it controls the starting and stopping of the oscillator 11 (see FIG. 1) by means of controlling AC-short-circuit conditions for the control winding 14 (see FIG. 1) in the same manner as indicated above in connection with FIG. 1. Also, the relay 26 and circuit connections 25 and 23 which were indicated in FIG. 1, are shown again in FIG. 2 y

In FIG. 2, the fast-reaction circuit related to the phototransistor 40 (see FIG. 1) takes a modified form over that illustrated in FIG. 1. Thus, in FIG. 2, the emitter connection 43 (see FIG. 1) from transistor 40 (FIG. 1) is applied to a terminal 71 that has a circuit connection 72 leading therefrom to one endof a radio-frequency chokecoil 73. The other. end of the coil 73 leads directly to the emitter of a PNP transistor 76. The base of transistor 76 is connected to the midpoint between a resistor 77 and a diode 78, which diode is one having a predetermined forward voltage drop in order to set the voltage on the base of transistor 76 at a desired level. The output of transistor 76 goes to the control circuit 32 and, as illustrated, this is via a cireuitconnection 81 that goes to the base of another transistor 82.

It has been discovered that by making use of the illustrated circuit, including the PNP transistor 76, a greatly reduced response time from the phototransistor 40 (FIG. 1) may be had. Because of the characteristics of transistors generally, and including phototransistors, there has been a difficulty encountered in highfrequency applications by reason of the loaddependent frequency response in regard to the phototransistors. Since a phototransistor is a current source, it is desirable to use a large-load resistance to develop maximum output voltage or to have high sensitivity. However, large-load resistances limit the frequency range which would mean longer response time for an ignition system. Thus, in the past, it has been considered necessary to compromise, i.e., trade voltage for speed, or vice versa. But, by applying the illustrated circuit to a control system according to this invention, a desired reduction in response time is created.

The coil 73 is part of a radio frequency filter, which includes a parallel resistor 85, along with a pairof capacitors 86 and 87, which are connected to ground and to the ends of the coil 73 as well as to the ends of resistor 85.

FIG. 3 illustrates a modification of the phototransistor circuit portion of the control circuit. It is applicable particularly to a system like that shown in FIG. 2. This arrangement permits elimination of a resistor, along with making use of the light-emitting diode for two purposes so that the diode 78 may also be eliminated.

Thus,in FIG. 3, there is a light-emitting diode 90 that is connected for energization from a circuit connection 91 which corresponds to circuit connection of FIGS. 1 and 2. Also,there is a temperature-sensitive resistor 94 that corresponds to resistor 53 of FIG. 1, and the radiation of light from dio'de 90 is directed toward a phototransistor 95 in the same manner as was described in connection with transistor 40 of FIG. 1.

In this instance, phototransistor 95 has its emitter connected directly to the emitter of a PNP transistor 98 that corresponds with transistor 76 of FIG. 2. In the FIG. 3 modification, the base of transistor 98 is connected via a connector 99 to a junction between resistor 94 and diode 90. The collector of transistor 98 goes directly to the base of another transistor 102 which corresponds to the transistor 82 of FIG. 2.

By making use of a circuit according to FIG. 3, the resistor 77 (FIG. 2) as well as the diode 78 (FIG. 2) may both be eliminated since resistor 94 and the lightemitting diode 90 take their place. However, it should be noted that where the circuit as indicated in FIG. 3 is employed, the elements shown must be physically located on or at the distributor (not shown) of the engine, in the manner indicated in connection with FIG. 1. In other words, when the FIG. 3 modification is employed, there is a distributor-located unit 105 which is indicated by the dashed lines around the circuit elements illustrated in FIG. 3. A 1

While the invention has been described above in considerable detail and in accordance with the applicable statutes, this is not to be taken as in any way limiting the invention, but merely as being descriptive thereof.

I claim:

1. In combination with an internal combustion engine, an ignition system wherein said system employs controlled-duration continuous-wave high-frequency spark energy,

said spark energy being generated by an oscillator having an output transformer and having a control winding thereon for starting and stopping oscillation of said oscillator at the beginning and end of each spark interval,

electronic switch means connected in series with said control winding for breaking and making a loading circuit which includes said control winding,

said spark intervals being determined by photoelectric engine-timed means including a phototransistor,

said electronic switch means having a control circuit therefor including said photoelectric engine-timed means,

circuit means for connecting said phototransistor in a common-collector configuration relative to said control circuit for minimizing the response time of said phototransistor.

2. The invention according to claim I-, wherein said improvement means also comprises means for connecting the emitter of said phototransistor to a prebiased base of an input transistor of said control circuit.

3. The invention according to claim 1, wherein said improvement circuit means also comprises means for connecting the emitter of said-phototran-v sistor to the emitter of an input transistor of said control circuit. t 4. The invention according to claim 3, wherein said means for connecting said emitters comprises a radiofrequency filter for blocking radio-frequency signals generated by said spark energy.

5. The invention according to claim'2, wherein said improvement circuit means further comprises reactance means in the output circuit of said input transistor for by-passing and blocking radiofrequency signals generated by said spark energy. 6. The invention according to claim 3, wherein said improvement circuit means also comprises diode means in the base circuit of said input transistor, said diode means having a predetermined forward voltage drop in order to provide a desired voltage level to said input transistor.

7. The invention according to claim 1, wherein said photoelectric engine-timed means comprises a light-emitting diode.

8. The invention according to claim 7, wherein said improvement circuit means also comprises means for connecting the emitter of said phototransistor to the emitter of an input transistor of said control circuit.

9. The invention according to claim 8, wherein said means for connecting said emitters comprises a radio-frequency filter for blocking radio-frequency signals generated by said spark energy.

.10. The invention according to claim 8, wherein said improvement circuit means also comprises diode means -,in the base circuit of said input transistor,

said diode means having a predetermined forward voltage drop in order to provide a desired voltage level to said input transistor.

11, The invention according to claim 10, wherein said means for connecting said emitters comprises a radiofrequency filter for blocking radio-frequency signals generated by said spark energy.

12. The invention according to claim 10, wherein said diode means comprises said light-emitting ;diode. 13. In combination with an ignition system for an in-.

ternal combustion engine, wherein said system employs controlled-duration, continuous square wave, highfrequency spark energy,

said spark energy being generated by a squarewave oscillator having an output transformer, and having a control winding thereon for starting and stopping oscillation of said oscillator at the beginning and end of each spark interval, electronic switch means connected in series with said control winding for breaking and making a loading circuit which includes said control winding, said spark intervals being determined by photoelectric engine-timed means 'comprising a lightemitting diode and a phototransistor, I said electronic switch means having a control circuit therefor including said phototransistor, the improvement comprising first circuit means for connecting said phototransistor in a commoncollectorconfiguration relative to said control circuit, second circuit means for connecting the emitter of said phototransistor to the emitter of an input transistor of said control circuit, said second circuit means including a radiofrequency filter for blocking radio-frequency signals generated by said spark energy, third circuit means including a temperature-sensitive resistor for energizing said' light-emitting diode in order to compensate for change in ambient temperature at said engine-timed means, fourth circuit means including said light-emitting diode having a predetermined forward voltage drop and connectingsaid diode to the base of said input transistor, all whereby said ignition system has improved response to the engine-timed spark-control means including temperature compensation and radiofrequency signal rejection. 

1. In combination with an internal combustion engine, an ignition system wherein said system employs controlled-duration continuous-wave high-frequency spark energy, said spark energy being generated by an oscillator having an output transformer and having a control winding thereon for starting and stopping oscillation of said oscillator at the beginning and end of each spark interval, electronic switch means connected in series with said control winding for breaking and making a loading circuit which includes said control winding, said spark intervals being determined by photoelectric enginetimed means including a phototransistor, said electronic switch means having a control circuit therefor including said photoelectric engine-timed means, circuit means for connecting said phototransistor in a commoncollector configuration relative to said control circuit for minimizing the response time of said phototransistor.
 2. The invention according to claim 1, wherein said improvement means also comprises means for connecting the emitter of said phototransistor to a prebiased base of an input transistor of said control circuit.
 3. The invention according to claim 1, wherein said improvement circuit means also comprises means for connecting the emitter of said phototransistor to the emitter of an input transistor of said control circuit.
 4. The invention according to claim 3, wherein said means for connecting said emitters comprises a radio-frequency filter for blocking radio-frequency signals generated by said spark energy.
 5. The invention according to claim 2, wherein said improvement circuit means further comprises reactance means in the output circuit of said input transistor for by-passing and blocking radio-frequency signals generated by said spark energy.
 6. The invention according to claim 3, wherein said improvement circuit means also comprises diode means in the base circuit of said input transistor, said diode means having a predetermined forward voltage drop in order to provide a desired voltage level to said input transistor.
 7. The invention according to claim 1, wherein said photoelectric engine-timed means comprises a light-emitting diode.
 8. The invention according to claim 7, wherein said improvement circuit means also comprises means for connecting the emitter of said phototransistor to the emitter of an input transistor of said control circuit.
 9. The invention according to claim 8, wherein said means for connecting said emitters comprises a radio-frequency filter for blocking radio-frequency signals generated by said spark energy.
 10. The invention according to claim 8, wherein said improvement circuit means also comprises diode means in the base circuit of said input transistor, said diode means having a predetermined forward voltage drop in order to provide a desired voltage level to said input transistor.
 11. The invention according to claim 10, wherein said means for connecting said emitters comprises a radio-frequency filter for blocking radio-frequency signals generated by said spark energy.
 12. The invention according to claim 10, wherein said diode means comprises said light-emitting diode.
 13. In combination with an ignition system for an internal combustion engine, wherein said system employs controlled-duration, continuous square wave, high-frequency spark energy, said spark energy being generated by a squarewave oscillator having an output transformer, and having a control winding thereon for starting and stopping oscillation of said oscillator at the beginning and end of each spark interval, electronic switch means connectEd in series with said control winding for breaking and making a loading circuit which includes said control winding, said spark intervals being determined by photoelectric engine-timed means comprising a light-emitting diode and a phototransistor, said electronic switch means having a control circuit therefor including said phototransistor, the improvement comprising first circuit means for connecting said phototransistor in a common-collector configuration relative to said control circuit, second circuit means for connecting the emitter of said phototransistor to the emitter of an input transistor of said control circuit, said second circuit means including a radio-frequency filter for blocking radio-frequency signals generated by said spark energy, third circuit means including a temperature-sensitive resistor for energizing said light-emitting diode in order to compensate for change in ambient temperature at said engine-timed means, fourth circuit means including said light-emitting diode having a predetermined forward voltage drop and connecting said diode to the base of said input transistor, all whereby said ignition system has improved response to the engine-timed spark-control means including temperature compensation and radio-frequency signal rejection. 